STERNA. 



723 



while all the rest of the upper part is bluish ash, with 

 the exception of the wing-coverts, which are brownish 

 with cross bars of black and white. The quills of the 

 wings and all the under parts of the body are, at this 

 season, pure white ; the feet are black, and the bill is 

 vermilion red. Whether these are the winter colours 

 which the birds uniformly assume in those places 

 where they are numerous and native, has not been 

 ascertained ; but it is probable that they are. When 

 full-grown, there is not understood to be much differ- 

 ence in the appearance of the sexes, either in the 

 summer or the winter ; but the young birds have 

 those parts which are ash-coloured in the adults 

 mottled with black, 



THE SANDWICH TERN (S. Boysii). This is a spe- 

 cies of the principal habitat of which there is not 

 much known, the chief notice that we have of it being 

 as rather a rare bird on the south-east coasts of Eng- 

 land, though it is probable that it breeds there, not, 

 however, in any considerable numbers. It is a bird 

 of a foot and a half in length, and about two feet nine 

 inches in the extent of the wings from tip to tip. 

 The back and the coverts of the wings are grey ; the 

 principal quills have the shafts and inner webs white, 

 and the outer webs mottled with small dots of black. 

 The top of the head, as far down on the sides as the 

 eyes, and backward to the nape, is black. The under 

 parts are white, with a blush of rosy colour on the 

 fore-neck and breast, which vanishes in the w inter, at 

 which time the head also becomes more or less 

 mottled with white, or white altogether. 



This species is usually found upon marshy places 

 near the sea, and it is particularly abundant in Hol- 

 land, and along the low shores of Germany. Its 

 chief subsistence is small fishes, which it captures 

 with great ease and readiness while driving about on 

 the wing. It is not found at any distance inland, or 

 far out at sea. 



THE LESSER TERN (S. minuta). This bird is very 

 generally distributed over the temperate and the cold 

 parts of the northern hemisphere ; but in the eastern 

 continent and in America, the long dreary beaches 

 of sand or shingle are the places over which it is 

 usually found ; andjt adds considerably to the inter- 

 est'of places that, have not very much to recommend 

 them, by the rapidity of its movements and the plain- 

 tive wailings of its voice. It is between eight and 

 nine inches in length, and more than a foot and a 

 halt' in the stretch of the wings. The upper parts of 

 the body, the wings, and the tail, are pale grey; the 

 quills of the wings being a darker shade of the same 

 colour. The top of the head, the hind head, and a 

 streuk from the gape to the eye, are black, and the 

 forehead and all the under parts of the body pure 

 white. The young birds are, however, very differently 

 coloured from the ad'ults, so that they are liable to be 

 mistaken for another species. The head is then 

 mottled with black and grey ; the back with grey and 

 yellowish white. The tail in the young state is very 

 little forked. 



These birds remain on the beaches all the year 

 round, though they are more scattered in line in the 

 winter, and collect into parties, on the grounds best 

 adapted for their breeding, in the summer. The 

 breeding time, for it cannot be called a nesting time 

 with them, is during the warmest time of the year. 

 The eggs are placed on the bare ground among the 

 pebbles of the shingle, and it is probable that the 

 heat of the sun during the day assists in hatching 



them ; for, even where there are a considerable number 

 of birds careering about on the wing, it is very rare 

 indeed that a female is started from her eggs, and 

 thus the birds afford no clue to such as seek for 

 them. During the night, however, it is understood 

 that the female sits, and that she sits also during the 

 day in case of rain. The eggs are only two, or at 

 most three, and they are placed in a little depression 

 of the sand or small gravel; they are pale brown, 

 and spotted over with dusky and ash-coloured 

 blotches. 



Though this tern is far from rare on the sandy and 

 shingly margins of the sea, and also of the great inland 

 lakes of the eastern continent, it has nowhere been 

 so closely observed or so faithfully described as by 

 Wilson. It arrives, that is, collects upon the spots 

 favourable for breeding, on the coast of the American 

 States, about the end of April. It " coasts along the 

 shores, and also over the pools in the salt maishes, 

 in search of prawns, of which it is particularly fond ; 

 ikOvcrs, suspended in the air fora few moments above 

 its prey, exactly in the same manner as some of our 

 small hawks, and dashes headlong down into the 

 water, generally seizing it with its bill, mounts in- 

 stantly to the same height, and moves slowly along 

 as before, eagerly examining the surface below. 

 About the 25th of May, or the beginning of June, 

 the female begins to lay. The eggs are dropped on 

 the dry and warm sand, the heat of which, during the 

 day, is fully sufficient for the purpose of incubation. 

 The heat is sometimes so great that one can scarcely 

 bear the hand in it for a few minutes without incon- 

 venience. The wonder would therefore be the greater 

 should the bird sit on her eggs during the day, when 

 her warmth is altogether unnecessary and perhaps 

 injurious, than that she should cover them only during 

 the damps of night and in wet and stormy weather." 



From this Wilson draws the conclusion which 

 almost any one would have drawn at the time when 

 he wrote, namely, " that the actions of birds are not 

 the effect of mere blind impulse, but of volition, 

 regulated by reason, depending- on various incidental 

 circumstances, to which their parental cares are ever 

 awake." Now that this tern is not guided by any- 

 thing that we call an impulse, either blind or not 

 blind, is perfectly true. A blind impulse is an attempt 

 to proceed in ignorance in a matter where knowledge 

 is absolutely necessary, while an impulse which is not 

 blind, or, as we may call it, a rational impulse, is one 

 in which the party proceeds upon a well-established 

 ground of experience. The bird cannot proceed in 

 either of these ways; for that which cannot acquire 

 experimental knowledge can never be said to be igno- 

 rant, for we are ignorant of nothing which is not 

 know-able, or to the right performance of which 

 experience would not be a certain guide if we were 

 in possession of that experience ; but the bird has no 

 need of experience. The young bird which never 

 saw an egg, performs her incubation in exactly the 

 same manner, and as perfectly free from mistake or 

 error, as the mother of a dozen of broods ; and it 

 would be just as vain to speak about an ignorant bird 

 blundering in its incubation, as to speak about an igno- 

 rant stone forgetting the way to fall after it were half 

 way down the pit or the precipice. It is much to 

 be regretted that even the very best books on the 

 natural history of animals are vitiated by the frequent 

 occurrence of this false philosophy, which instils the 

 very worst of errors often with the best intentions, 



